Wiktionary
n. The start of the fifth hour of the day in both the 12-hour and the 24-hour clock; 4:00.
WordNet
n. any of several plants of the genus Mirabilis having flowers that open in late afternoon
Usage examples of "four o'clock".
When I left the room at night the time-clock was set to open at four o'clock the following afternoon.
On each occasion I was at the house previous to four o'clock and had to wait a few minutes before I could enter the room.
By four o'clock in the afternoon, viewers in the Delaware Valley were going to wrinkle their noses and wonder why she'd been picked to host a new talk show.
First Sarah's baby, then the fight, then getting Sophie out of trouble and, believe it or not, the Diamond T holds out and we don't see a cop the whole way and get back to Yankalillee at four o'clock in the afternoon.
The short summer night waxed slowly brighter until, toward four o'clock, daylight drowned the last stars.
Pierce Keswick had been in his Nashville office at four o'clock and had died in Maggody within the next eleven hours.
And that was very likely the last time Roger had known what time it was-if he had been sufficiently conscious to hear one of the Army surgeons announce that it was then four o'clock-and to give his considered opinion that Roger would not live to see the hour of five.
I made for Covent Garden Market, because this is one of the places in London where a man may be seen at four o'clock in the morning without exciting suspicion.